Warning signal for fluid brakes



March 16, 1954 R 5 MacDQNALD 2,672,535

WARNING SIGNAL FOR FLUID BRAKES Filed June 17, 1952 BY Q ZY Patented Mar. 16, 1954 UNITED OFFICE WARNING SIGNAL FOR FLUID BRAKES Robert B. MacDonald, Hagersville, Ontario, Canada Application June 17, 1952, Serial No. 294,030

2 Claims.

This invention relates to improvements in warning signals of the kind which cause the operator of a motor vehicle to become immediately conscious of a drop in the level of the brake fluid in the reservoirs of the master cylinders of fluid braking systems beyond the maximum required for safety. More particularly the invention contemplates an improved switch for automatically closing an electric circuit, whereupon a signal, which may be either a visible or an audible signal, becomes energized when the fluid by reason of any of the common causes reaches a lower level than that which has been predetermined a safe level.

The invention consists essentially of a switch box mounted externally of the reservoir, the circuit closing element of which is loosely connected to the upper end of a plunger vertically reciprocal in the sleeve of a certain swivel, the plunger extending internally of the reservoir where it is pivotally connected to the arm of a float, the arm being also pivotally connected to a certain portion of the swivel which also extends into the reservoir.

Different makes of motor vehicles have differently proportioned brake fluid reservoirs, varying particularly in the diameters of their filling openings and plugs, the smallest being approximately seven-eighths of an inch. In reservoirs having wide openings it has been an easy matter to insert, or install, one of the common types of float operated switches, but such has not been true with reservoirs having the smaller openings, obviously because of the bulky character of those elements of the accessory which have to be inserted through the opening and disposed inside the reservoir.

An important object of the invention is to provide a float operated switch, the float and the float components of which may be easily introduced through the smallest known filling openings of brake fluid reservoirs.

Another important object is to provide means whereby, regardless of the rotary position of the switch box, that is, no matter where the switch box happens to stop when screwed home into the filling opening, the float and the float arm will be aimed or located in their proper place and will not become damaged in any way by the turning of the switch box.

Another important object is to provide novel means whereby establishment of even contact between the circuit closing element and certain terminal posts is assured, regardless of structural fault and the variance of the axis of the plunger ofl vertical.

A fourth important object is to provide a device of the kind specified which is manufactured in a single unit that is, with no separable parts, and so may replace the conventional filling opening plug simply by screwing out the one and screwing in the other.

A fifth important object is to provide a device of the class described which will be simple, durable, effective, and inexpensive to produce.

These together with other objects which may later apear may be attained by the structure and combination of parts which will be hereinafter fully described, specifically claimed, and illustrated in the accompanying drawings in which like reference characters refer to like parts throughout the several views and in which:

Figure 1 is a. partial sectional elevation of a device as constructed in accordance with this invention, the adjacent portion of the fluid reservoir being partially shown and also in section.

Figure 2 is a reduced sectional elevation of a typical fluid reservoir showing the switch unit in the position of being introduced into place.

Figure 3 is an enlarged detailed elevation of the circuit closing element and the upper portion of the plunger.

Figure 4 is an enlarged top view of the circuit closing element.

Figure 5 is a cross-sectional elevation taken on the line 5-5 of Figure 4.

Referring now to the drawing, the fluid reservoir is indicated by R, its filling opening by RA.

In its present embodiment the invention consists of a switch box in the form of a cup it which preferably has flat opposed external faces, here shown as a hexagon, for receiving a wrench. The cup is extended downwardly in a reduced externally threaded base l2, which may well be termed a plug portion, which replaces the original plug in the filling opening when the switch is installed.

The cup Ill is closed by means of a disc I3 of insulation (non-conductive) material, and extending through this disc from the outside to the inside of the cup are spaced electric terminal posts M. In practice, wires (not shown) are connected to these posts and lead through a power source (not shown) to an alarm or signal (not shown) which may be conveniently located within the vision or earshot as the case may be, of the vehicle operator.

A swivel consisting of a sleeve l5, which is preferably thimble-like, journaled in an opening I6 in the base portion 12, and a yoke l1 beneath and carried by the sleeve, is adapted to remain stationary while the cup turns when being screwed into the reservoir. Through the sleeve I 5 extends a plunger l8, on the upper end of which is provided a pair of collars [9. Between these collars, and loosely free to revolve on the plunger, is a circuit closing element consisting of a disc 20. The collars are so spaced as to permit the disc the freedom to tilt in any direction, and the internal diameter of the sleeve is enlarged toward the bottom in order to afiord the :plungera slight wobble.

The disc or circuit closing element 20 is formed of stiff insulation (non-conductive) material,

and inlaid in the upper face ofathisadisc zis asring 2] (see Figs. 4 and 5) of conductive material. The mean diameter of this ringequalsthedistance between the axes of the posts 14.

Pivoted to the yoke as at 22 tand againiat the,

lower end of the plunger l8 as at 23, is an arm 24 which carries a float 25 at its free end. The arm is, in effect, a lever to which reciprocal movement of the [plunger 4d, and hence vthe :dlsc 1120, are responsive. The :arm may be extensible by means of a ltelescoping istructure as shown.

Thmmenibers which reside within :the .reservoir, namely, th'e float 25 .and the yoke 1 1, :are less in girth than the diameter .of thereservoir filling opening, .and itheretore :the assembly may be easily. inserted-by 1 introducing; it-float :first in an arcuateipath as illustrated in :Fig. 22and indicated loy the :arrow ithereon. The cup is then screwedtintotplacemnd because of theswivel the float-assembly will notiturn with the cup. 1 0bviously the .device may be as easilytremovedtfor recharging thebraking system.

operation, assuming #that :the levelof the fluid inzthe reservoir has: iallcnvappreciably below maximum==but not to -the danger' pcint, thedloat having also tallen has elevated -the plunger l8 and the discmlgthe'ring z lof the latter into contactfl with the posts- Mpthe circuit becomes closed andtheialarm energized.

The-discs! Ii -is looselyiconnected to the plunger, and thereflore -tiltable, in order to assure even "contact with botmposts should 1 the axis or the plunger be outi:ot parallel with that of the cup;

or with that of the posts, or should there happen to be disparities in the position of the posts.

I claim:

1. In a fluid level controlled switch, a cup having a threaded base portion, a pair of terminal posts extending into the cup through a nonconductive cup closure, a swivel comprising a sleeve journaled in said base portion and a yoke beneaththe sleeve, 9. plungerprecinrbcally operable in the sleeve, a circuit closing element in the cup and loosely carried by the plunger, and

'an arm having buoyant means at its free end and pivoted to :the poke at one point and to the plunger at another point, said circuit closing eleilfi ment including "a disc loosely rotatable on the plunger between a pair of collars, the space betwesn,-.the;collars being greater than the thickness of the disc.

In afifluid level controlled switch, a cup having a threaded base portion, a pair of terminal posts"extendingwinto;the.zcupqthmughrarmonecnnductive c.up. clcsure,,; a swivehineludihg a isleeye journaled in said; :base-.:portion; a plunger 01181;- able in the sleeve, agcircuitt-closing aelemcntxin cup and loosely carried by the 19111118611, buoyant; means associated :with :the plun er :for elevating the, circuit [closing tclement. intercontact with the terminal posts :1 onrthe, dwphin mf a fluid level,-. said acircuit-aclosingeelement:including a discloosely rotatablezthennlufigerthep tweena pairtof collarsttthfi SW6 zbetweemthe collars being greater fthanslthe thiclmessmfj-ythe disc.

References cued-1m. the fileOftNsQflknt UNITED "STATES PATENTS Number Name .391.

1,095,311 s rfing..-"wuinqm 5,. 1.914 1,481,470 ,La :Londe Jan 22, 1824 1,712,665. .Gregory -,May 11$. k g29. 2,074,260 Gerow ,,.Mar. 16,-,19357 2,520,237 ..C1Bai! A1 1 E,-;,29'. lr950 

